: Four Billion Years of Microbial Evolution
by: Lynn Margulis + Dorion Sagan
publisher: University of California Press 1997 
other: 300 pages, index, US$11.95
Microcosmos tells the story of life on Earth from its origins down to the present, with a focus on what Stephen Jay Gould calls "the modal bacter", on the central role played by bacteria and other microbes. At times the stress on these is hyberbolic, as indeed the preface to this 1997 edition pretty much admits. That preface suggests that this was intended to counter ecological arrogance and to balance human-centric ways of looking at the world.
As well as looking at things from a microbial perspective, Margulis and Sagan place a stress on the role of symbiosis and cooperation in evolution that would have pleased the anarchist Kropotkin. Margulis was largely responsible for reviving the now generally accepted endosymbiotic theory for the origin of mitochondria and chloroplasts, and that is one of the topics covered. It is also suggested that the "cell whips" or undulipodia which play such an important role in cell and chromosomal movement originated as free-living spirochetes.
In some places, however, Microcosmos borders on outright mysticism, with a confusion of levels of understanding: "The reality and recurrence of symbiosis in evolution suggests that we are still in an invasive, 'parasitic' stage and that we must slow down, share, and reunite ourselves with other beings if we are to achieve evolutionary longevity." And though Margulis and Sagan are excellent guides to the bacterial world, they are not so good when it comes to human evolution. Here they make a few quite egregious errors, such as "all primates today except ourselves are vegetarians or insectivores", and in general their account appears to have been cribbed from popular works on the subject.
So I had mixed feelings about Microcosmos. While it should be read with a critical eye, however, and I would hesitate to recommend it to a complete newcomer to evolutionary biology, it is nevertheless most enjoyable and informative. There is far more to it than the few items I have singled out above.
Disclaimer: I requested and received a review copy of Microcosmos from the University of California Press, but I have no stake, financial or otherwise, in its success.